Stepped bottom and variable frame cross section powerboat hull

ABSTRACT

It concerns a hull made up of three (3) sections of different draught, width and design each. The front section (F) is larger than the middle (M) and the rear section (R), while the middle is larger than the rear. The hull sections are divided between them by a transverse rib ( 5 ). In the front, instead of having stabilizer fins, there are four oblong ribs ( 3 ) on each side. In the middle there are three oblong ribs ( 3 ) while in the rear there is one oblong rib ( 3 ) and two stabilizing fins ( 6 ) on each side. The advantage of this invention is the acquired capability of the powerboat to achieve higher speed, with less power and fuel economy, as there is a great reduction in friction due to the hull&#39;s design.

The invention concerns a stepped-draught and variable limber-hole hull, used in the manufacturing of any type of powerboat.

It is a cohesively manufactured hull made up of three (3) sections of different draught and width each and of different design.

The boat's hull, (together with the motor), is responsible for cruise security, quality and speed, fuel consumption and therefore the cruise range. A necessary precondition for safe and easy cruising of a boat is its ability to cruise with the less possible friction between the hull and the water. A boat's ability to skid at very low speed is an important factor for safe and easy cruising under tough weather with great waviness.

The hulls known to us today are characterized by the fact that the V-angle at their front section decreases evenly towards the rear end of the hull.

All the common powerboat hulls lift their front section at a large angle when starting to cruise, exactly because of the properties of their design. Followingly, assisted by the motor, they manage to relatively align the front section of the hull with the water surface and to keep a large section of the hull out of the water, thus creating a skidding effect.

In order for a boat with a common hull to skid, it is necessary to have great motor power when starting to cruise. During great waviness, boats with common hulls, in order for them to skid, they have to maintain high speed, which results in the hull's fierce clash with the waves. This gives intense tramps to the boat.

The clash is usually fierce exactly because of the reduced speed imposed by the waviness, as the front section of the hull rises at a large angle relatively to the water's surface and then hits the surface about the middle of the hull, where the V-angle is much smaller than that of the front. Thus, in order to achieve safer and easier cruising under great waviness, the speed must be reduced. This makes the boat cruise without skidding and exerts pressure on the boat's motor resulting in higher fuel consumption.

As known, the cruise quality of a powerboat depends on the length of the waterline in water. The greater the length of the waterline in contact with the water is, the better and safer becomes the cruising. Common powerboat hulls are designed in such a way that the more the cruising speed is, the smaller their awashed surface is. When the awashed surface is seriously reduced because of the speed, the boat loses its stability. Therefore, in wavy conditions, the boats with a common hull have their in water waterline noticeably shortened, when trying to achieve high speed, and as a result the cruising becomes bad and insecure. The advantages of the present hull as presented, are achieved thanks to its design, which divides it into three different sections, each of which is designed separately.

The front section of the hull (F) is characterized by the very big transverse V, which begins at sixty-nine degrees (69°) in the front and bottom section of the hull (1) and ends up at forty degrees (40°) in the rear and bottom area of the front section of the hull (2). This section of the hull develops gradually towards the upper area with the existence of four oblong ribs (3). Therefore, the front section of the hull, despite its very large V at the bottom, can achieve the largest width at the upper section of the hull, 1.75 m. (4), with the four oblong ribs. At the front section of the hull, the four oblong ribs basically replace the stabilizing fins usually fit into other boats (Patterns 1.1, 1.2, 1.3, 1.4).

Thanks to the large V, the hull comes into contact with the water at a small face area. Result of this is that in especially heavy waviness, tramping, due to the hull's collision with the wave, is avoided, and because of limited floating, the hull does not skid.

The middle section of the hull (M) is different from the front, as it is at a different level from it. It is separated from the front section of the hull by a transverse rib (5), created by the draught difference between the front and the middle section of the hull. Thus, the two sections of the hull create a kind of recess at the point of pattern difference. The middle section has three longitudinal ribs (3) and only one (1) stabilizing fin (6) above the first oblong rib. The middle section of the hull, at its lowest point (7) has a V that begins at the contact point with the front section of the hull at forty degrees (40°) and ends up at the rear (8) at twenty-seven degrees (27°). The three oblong ribs of the middle section of the hull (3) form the continuation of the oblong ribs of the front section of the hull. (Patterns 2.1, 2.2, 2.3).

Because of the fact that the middle section of the hull is in essence a recess compared to the front section, during cruise, it comes into contact with smaller quantities of water than does the front section. This is achieved with the crosscut rib, which works as a step. Thus, during cruise, the water quantities that flow into front section of the hull are pushed, thanks to the crosscut rib, to an area of the middle section of the hull. Therefore, the surface of the hull that comes into contact with water is smaller than that of common hulls. This results in maintaining high speed during waviness, but without tramps and lifting as with hulls known to us today.

The rear section of the hull (R) is also a recess in relation to the middle section. It is at a different level from the front and middle section and it is separated from the middle by a crosscut rib (3). The rear section of the hull starts with a V of twenty-seven degrees (27°) at the point of contact with the middle section of the hull (8) and ends at the boat's mirror at an oval surface (9). The rear section has only one oblong rib (3), from each side, which is near the hull's tail (9), while there are stabilizing fins (6) put in the imaginary line of the ribs of the hull's middle section. (Pattern 3.1, 3.2, 3.3).

All the oblong ribs and fins of the middle and rear section of the hull are put at a distance from the transverse ribs that separate the hull's sections. The distance varies depending on their position on the body of the hull. This way, a reduction of the hull's flat surfaces is achieved coming into contact with water during cruising, thus resulting in a reduction of tramps.

Because of the large flat surfaces on the rear section of the hull, great hydraulic pressure is developed, which pushes the rear section of the hull upwards. This pressure is particularly strong at the section of the hull near the mirror. This results in the boats skidding at low speed and directly. Simultaneously, due to the great hydraulic pressure developed at the rear of the hull, the rear section's draught is avoided and as a result its front section (bow) does not easily rise. Thus, the boat can cruise at high speed under wavy conditions, without carrying large loads, and the cruise angle of the boat and its speed are not altered.

With these characteristics, the hull of this invention achieves a reduction of the friction caused by motion on the water's surface, at a rate that exceeds 50% of the friction caused by common hulls (Patterns 4.1, 4.2).

The result is that the boat using this hull needs less horsepower from the motor in order to cruise at the same speed boats with greater horsepower do, with, however, a common hull. There is also a decrease in fuel consumption necessary for the boat to cruise with the hull of the present invention, as it achieves a speed similar to that of a common hull boat, yet requires a less powerful motor.

This hull is made up of three unequal sections and has the ability to cruise at great speed, even under waviness, because the front section, which has larger dimensions than the other, basically opens the corridor from where the other sections pass, which go through the water at greater speed and less friction due to their smaller size.

The hull of the present invention, thanks to its construction, undergoes less strain than common hulls. This allows a lighter structure in its inner supports, thus giving the boat a lighter weight than those with a common hull. 

1. The stepped-draught and variable limber-hole hull used in the manufacturing of all kinds of powerboats is made up of three sections (F) (M) (R), which differ in draught, width and design. The front section (F), instead of stabilizing fins, has three oblong ribs (3) on each side. The front section (F) has a sixty-nine degree (69°) V at its lowest point (1), which decreases reaching forty degrees (40°) at the point of contact (2) with the middle section of the hull (M). The middle section of the hull (M) has a smaller draught than the front. It is separated from the front with a crosscut rib (5) created by the draught difference between the front and the middle section of the hull. The middle section has three oblong ribs (3) and only one (1) stabilizer fin (6) over the first oblong rib. The middle section of the hull at its lowest point (7) has a V starting from the point of contact with front section of the hull, from forty degrees (40°) and ends at the point of contact with the rear section of the hull (8) at twenty-seven degrees (27°). The rear section of the hull (R) forms a recess compared to the middle section. It has a smaller draught than the front and middle sections and is separated from the middle section with one oblong rib (3). The rear section of the hull begins with a V of twenty-seven degrees (27°) at the point of contact with the middle section of the hull and ends at the boats mirror at an oval surface (9). The rear section has only one oblong rib (3) from each side, which is near the tail of the hull (9), while there are stabilizing fins (6) put on the imaginary line of the ribs of the hull's middle section.
 2. The powerboat hull is characterized according to claim 1 by its four oblong ribs (3) on each side of its front section (F), three oblong ribs and one stabilizing fin on each side of the middle section (M) and one oblong rib (3) on each side of the rear section (R).
 3. The powerboat hull is characterized according to claim 1 by the fact that its three sections are separated by two crosscut ribs (5) creating recesses. Therefore, the middle section (M) is a recess compared to the front section of the hull (E), and the rear section (R) a recess compared to the middle section of the hull.
 4. The powerboat hull is characterized according to claim 1 by the fact that despite its sixty-nine degree V at its front section, the existence of oblong ribs instead of stabilizing fins gives at its upper tail the dimension of 1.75 m.
 5. The powerboat hull is characterized according to claim 1 by the fact that the oblong ribs of the middle section of the hull, the stabilizing fin of its middle section and the stabilizing fins of the rear section are on an imaginary line with the oblong ribs of the front section, but they begin their stretch at a distance from the crosscut ribs that separate the hull's sections.
 6. The powerboat hull is characterized according to claim 1, 2, 3 and 4 by the fact that during cruising it achieves a reduction of friction created by movement on the water's surface at a rate over 50% of the friction created by common hulls.
 7. The powerboat hull is characterized according to claim 1, 2, 3, 4 and 5 by the fact that its front section is of larger dimensions than the other sections, creating during cruise a passage for the other sections to pass through, which because of their smaller dimensions run through the water at a higher speed and less friction.
 8. The powerboat hull is characterized according to claim 1, 2, 3, 4, 5 and 6 by the fact that it is under less stress than common hulls, and this allows a lighter structure in its inner supports, so the total final weight of the boat is lighter than that of the boats that use common hulls. 